From time to time, orthopedic implants such as a knee replacement and the tissue around the implant can become infected. The infected implant is removed, and it conventionally takes four to eight weeks or more to adequately treat the infection during which time the implant site is kept immobile. This may cause unused muscles to contract and shrink the space previously occupied by the joint implant that connected articulating bones such as the space between the end of a femur and the tibia bone in the case of a knee replacement.
To prevent the shrinkage of the implant site, one treatment is to replace the infected permanent implant with a temporary implant or spacer made of an antibiotic-filled cement to fill the void. The spacer preserves the distance between the adjoining bones so that muscle cannot overly contract while the infection is being cleared from the implant site. Additionally, once positioned within the body, the antibiotic leaches out of the spacer to treat tissue near the spacer and prevent further spreading of the infection. The spacer is usually left in the void for four to eight weeks, but can be implanted for up to six months to clear the infection. Once the infection is cleared, the spacer is replaced with a new permanent implant. Ideally this type of spacer will allow some movement and preserve joint spacing, but is not usually intended to support the loads encountered by healthy bone or permanent, long term implants.
Some known spacers are pre-made and are provided to the physicians performing the surgery. This usually provides little or no opportunity for the physicians to significantly customize or modify the spacer to match the size of a patient's implant site. The pre-made spacers also cannot be easily and quickly modified to change the implant configuration. For instance, the physician may at first desire a knee implant to have a medullar stem to be placed axially into a medullary cavity in the femur or tibia but then reverse that decision upon opening the implant site. At that point, however, it may not be convenient, or even possible, to remove such a stem from a pre-made knee implant.
Other spacers are molded by the physicians by filling molds with curable cement during the surgical procedure. In these cases, when hard molds are used, substantial customization is not possible when a mold is provided in one size and configuration. Also, relatively cumbersome, time consuming, and messy procedures are used to fill the molds. For instance, such hard molds are usually filled by pouring the antibiotic filled cement into mold pieces and then placing the cement into all spaces in the mold by using a spoon or spatula. In other cases, the molds are inserted in-situ at the surgical site and the implant is made while the mold is in-situ.
Other known relatively soft silicone spacer molds are enclosed for injecting cement into the mold from a cement gun with a nozzle. To fill all of the spaces in the enclosed mold, extra time and effort by the physician is required to shift and/or rotate the nozzle of the cement gun in different directions within the mold. Thus, a spacer mold is desired that permits physicians to easily and quickly select and adjust the size and configuration of the spacer mold, even while the implant site is accessible, and efficiently and cleanly fill the spacer mold.